>>18323208BW2 was international. It had pokes from all gens from the start. BW didn't in the start, so that protag favors those pokemon more. The BW protag isn't used to all those new Pokes. Also, the Unova starters all suck massive monkey balls so fuck them they don't deserve to be in anything that's canon.
I added mew2 in Reds team because this guy is aggressive and likes to win... but also has a soft spot for his weak Pikachu and completely unbalanced team. He keeps the strongest pokemon with him so that he can still win and still use his bros.
The GSC protag chose Chickorita because he likes cute stuff and just went with the cutest available. He caught the red gyarados and got a tyranitar because his team needed power. He built his team around balance and put a lot of thought into what he carries.
Emerald guy just chose the coolest starter and caught a bunch of local pokemon. He had a salamence but he keeps metagross because it's shiny and looks cool. Yeah this guy is pretty simple that way.
The DP protag just loves steel pokemon. So he filled his team with them and staraptor, which was his first pokemon caught. He keeps electivire and froslass because hes always been fascinated with traveling and those pokemon are from other areas.
BW just likes to reck your shit. Hes a dick. BW is a fag and likes to torture the opponents pokemon before finishing them of with sand abusers. A fucking sadist.